Method of bonding aluminum to a metal



L May 6, 195 J.HJ. DAILEY EIAL 2,833,668

METHOD OF BONDING ALUMINUM To A METAL .I w 22 v Joseph J- Dai/ey John E. Fax

INVENTORS Y I Aum y 6, 1958 J. J. BAILEY ETAL 2,833,668

' METHOD OF BONDING ALUMINUM TO A METAL Filed June 10. 1954 3 Sheets-Sheet 2 Joseph J. Bailey John E. Fox

IN VEN TOR S BY Ame May 6, 1958 J. J. DAILEY ETAL 68 METHOD OF BONDING ALUMINUM TO A METAL Filed June 10, 1954 3 Sheets-Sheet 3 I W ALLoy 42 J L 372104 YBDEUUM w METAL'LIZEU ALLOY STEEL RING- GROOVE {ROCKWELL C 23-26) JNVENTORS.

Josgp/z Bailey 0120 United States Pateflto 2,833,668 I METHOD or BONDING ALUMINUM TO A METAL Joseph J. Dailey, East Peoria, and John E. Fox, Washington, 111., assignors, by mesne assignments, to John Altorfer, Peoria, 111.

Application June 10, 1954, Serial No. 435,696

14 Claims. (Cl. 117-50) The present invention relates to an improved method of bonding two dissimilar metals together and to an improved article such as a piston for internal combustion engines produced in accordance with said method either as an original article of manufacture or as a repaired product.

For purposes of a better understanding of the invention, it is known that outwardly expanding rings of a comparatively hard metal are installed in circumferential grooves cut in the outer surface of pistons used in internal combustion engines. The first one or two rings near the head of the piston are generally referred to as compression rings and serve to block the escape of flame and hot gases developed during the compression and explosion strokes, whereas the rings further down towards the skirt of the piston are oil rings which check the passage of lubricant past the piston during its reciprocation.

Due to the intense heat to which the head of the piston is subjected, the aluminum stock around the compression ring tends to soften enough that between the friction with the cylinder wall resisting reciprocating movement of the compression ring and the inertia of the ring itself resisting reversal of its direction of movement under rapid recipro-. cation of the piston, the harder metal of piston ring hammers against the soft aluminum stock forming the sides of its groove and enlarges the groove. This hammering is further augmented by the gas pressure dynamics acting on the under side of the top ring with a force superior to inertia forces present which causes a ring flutter each expansion stroke. The hammering condition becomes worse and worse as the groove becomes wider and wider.

Endeavors have been made by others as well as ourselves to replace the hammered sides of the compression ring grooves with harder metals that would withstand the hammering of the ring and stay tightly in place only to find that because of different coelficients of expansion, bonding difiiculties, etc., the hard metal insert forming the groove works free, starts a hammering action of its own, and multiplies the hammering effect exerted-on the aluminum stock.

One of the objects of the present invention is to provide an improved method for bonding an alloy steel such as stainless steel to aluminum or an aluminum alloy.

A further object of the invention is to provide an improved bond between aluminum alloys and steel alloys which withstand hammering under temperatures approaching the annealing point of the aluminum alloy.

Another object of the invention is to provide an improved piston ring supporting groove construction which will stand up under the hammering of the piston ring in engines such as diesel railway engines for a hundred thousand miles or more without need for repair or replacement of the piston.

Another object of this invention is to provide a construction of a piston whereby the latter may be fabricated of aluminum or other light metals such as magnesium in accordance with conventional practice as often required in high speed engines to reduce piston inertia forces, and

yet may have a ring receiving portion of a relatively harder material permanently bonded thereto for minimizing deterioration between the piston rings and the sides of the piston ring grooves of the piston.

A further important object of the invention is to provide an improved and economical method whereby a hardened ring receiving portion may be incorporated in a light weight aluminum piston during the manufacture or repair of the same.

Still another object of the invention is to provide a piston construction whereby a ring receiving portion of relatively harder material may be incorporated in a light weight piston body in an improved manner'to provide a thoroughly satisfactorily sealing and retaining means for bonding the harder portion to the piston and to provide for effective heat transfer from the piston body to the rings and fromthere to the cooled walls of the cylinder.

These, together with various other objects and features of the invention, which will later become apparent as the following description proceeds, are attained by the present invention, a preferred embodiment of which has been illustrated, by way of example only, in the, accompanying drawings, wherein:

Fig. 1 is a vertical sectional view through a piston having the hardened ring receiving portions combined therewith in accordance with the principles of invention;

Fig. 2 is a horizontal sectional view taken substantially upon the plane indicated by the section line 2-2'0f Fig. 1; Figs. 3-8 are successive diagrammatic views indicating in vertical central section the various steps in the method harder materials are sprayed into and bonded to the knurled channels; Fig. 7 showing the piston at the completion of the spraying operation; and, Fig. 8 showing.

the outer harder material machined to the circumference of the piston and with the piston ring grooves machined therein ready for the reception of the piston rings and use in an internal combustion engine.

Fig. 9 is a side elevation of a piston showing the construction of the conventional piston ring grooves with the oil return holes in the bottom groove;

Fig. 10 is an enlarged partial section taken of the compression ring groove of the damaged piston machined ready for repair; i

Fig. 1 1 is a view similar to Fig. It) in which the intermediate layer of metal is applied;

Fig. 12 is a view similar to Figs. 9 and 10 in whichthe hard fill metal is applied;

Fig. 13 is a view similar to Figs. 9-12, inclusive, showing the recutting of the piston groove in the hard fill metal;

Fig. 14 is an enlarged view similar to Fig. 13 showing another form of.the invention wherein the walls of the repair groove had been roughened;

Fig. 15 is a micro photograph showing the respective layers of metal applied in Figs. 11 and 12.

Patented May 6, 8,

will be helpful in understanding the invention:

of metals The improved method of bopding two rnetal masses to each other comprises using an intermediate bonding materialwhose melting point ispreferably above the boiling point of one of the metals bonded and above the melting point of the other metal bondedl The intermediate material is sprayedinj molten condition at a temperature above itsmelting point againstsaid one metal to vaporize a thin outer. layer-thereof and deposit the sprayed material upon an unoxidized surface." vaporizing the thin outer layer removes oxides and surface impurities and with the sprayed metal solidifying first some of the vaporizedmetal condensesand solidifies on the outer surface of the intermediate material. Thereafter spraying the other metalin molten. condition on the. exposed intermediate material having the condensed metal. on its exposed surface, alloys the other metal withthecondensed metal to extent that such is there in quantity, and thereafter. the remaining amount of the other metal sprayed on is. pure and provides sutiicient StOQkzfQl finishing or machins'p p cs-fl More particularly we have found that by directing molten molybdenum against a body of aluminum warmed preferablyby infrared lamps'to approximately 450 F., particularly between adjacent walls disposed at an obtuse angle of approximately 100, a thin layer of molybdenum accordance with the present invention as set forth in the is depositedthat'isthoroughly bonded to pure aluminum without an intervening layer of oxidized aluminum. Stainless steel .;,is then sprayed against the molybdenum layer. anda layer ofxs'ubstantial thicknessof ferrous alumipp fil'ibcMnen.themolybdenum and .the layer of pure stainless steel. "Ihu s,jfr0m the three metals employed, four layers o f rnepgl resultbonded so intimately that crushtests disclose fraetures occurring, without respect to interfaces. This bond is established regardless of "whether the starting -suriae'e-i s smooth or roughened.

A particular applicationiof this process is madeinprovidingra novel aluminum piston for internal combustion engines in which the piston} ring is mounted in a groove cut in a hard metal insert permanently bonded to the aluminum stock of the piston.'

Present day internal combustion engines universally employ pistons of an extremely lightweight construction a such as aluminum, .alurninumalloy andcthe like. This material, while providing an extremely lightweight piston,

possessesthe disadvantage that the materialatfording the,

desired lightness is subject to high heat, and to a hammering by the relatively harder material ofthepiston rings disposedin the'pistonring grooves of the piston. As a result, numerous disadvantages arise during ope r ation ofi the engine because. of the excessivewear fof the piston ring grooves by the very hard material of the pistorifring s. v

This is a problem of long standing.

It istheprimary and basic purpose of this inventionlto overcome these disadvantages by incorporating inla light weight piston such as an aluminum piston a 'hard metal J portion containing ring receiving grooves 'whichportion i shall be of a relatively harder material than the pistonin' order to minimize grooveWearbyithe rings; and shall be bonded. to the piston in an improvedand more secure manner, and, shall have ayhighly desirable high rate.

of heat transfer from the rings to the body of the. piston.

accompanying drawings and in the following description.

Reference is now made specifically to the drawings wherein like numerals designate similar parts throughout the various views. The numeral 10 designates generally any conventional form of light weight piston such as one made of aluminum, an alloy or the like. The piston is provided with a customary head portion 12 and skirt portion 14 together with bosses 16 disposed diametrically opposite each other for receiving the conventional wrist pin or piston pin by which the piston rod or connecting rod (not shown) is secured to the piston and attaches the latter to the crankshaft of the engine when the piston is in working position in a cylinder.

The compression rings are indicated at 18 which serve to prevent escape of the pressure of the exploded gases between the piston and the wall of the cylinder, while the oil ring is indicated at 20 to prevent escape of oil upwardly past the piston and into the combustion chamber of the cylinder.

Referring now particularly to 1, it will be seen that there is provided a circumferential groove or channel 22 extending about the upper portion of the piston just below the piston head, this channel having outwardly diverging side walls. A similar channel 24 can be pro vided circumferentially about the exterior surface of the bottom portion of the piston skirt 14. The relative inclination of the walls of the channels is approximately 15 as indicated in Fig. 10 from a line 29 perpendicular in side elevation to the bottom of the groove 22 or 24. This tends to huddle the sprayed materialand provide the best angle for the interfaces under relative heat expansion.

In applying the metals as described, the piston chemically cleaned is preferably mounted on a turntable or lathe (not shown) with infrared lamps 40.directed against the piston 10 to bring the temperature ofthe entire body up to approximately. 450 F, its expected working temperature. This vaporizes moisture and any cleaning fluid that may remain and heat expands the aluminum to its normal working expansion. A conventional mctallizer or metal spraying gun 41 is loaded. with molybdenum and sprayed into the groove as at 42 to a depth of .0Ol5.003 of an inch at a temperature well above its melting point. Then preferably a stainlesss tee], having high chrome content and some nickel is loaded in the gun and as shown in Fig. 12 the groove is filled as at 43 with some overspray along the sides. Thereafter the overspray is ground ofl? to the diameter of'the piston preferably under coolant and the groove 30 cut by carbide tools under suitable coolant.

Vaporization of the oxidized surface of the aluminum places the molybdenum in intimate bonded relationship with unoxidized aluminum stock, the vaporized aluminum forming a temporary but protective atmosphere until the solidified aluminum is brought to a molten state to alloy with the first layers of the stainless steel being sprayed on in the next step. This diffusion develops a layer of x ferrous aluminate 44 which bonds well with the molybdenum and with the steel thatis being applied. After there is no more aluminum to alloy it, the stainless steel 43 applied is pure. This provides a very effective bond thataffords good heat exchange and an enduring groove for long periods of piston use.

As illustrated, several compression rings ls'are received in individual grooves c'utin a single annular body portion 26 ofhard material, while a single oil seal ring 20-.is shown carried by a lower body portion 28in the channel 24. Variousother arrangements of rings are possible. A single fill and channel can be provided for each ring or any other desired number of ringsmay be any desired dimension.

After the hard material 26 and 28 is secured in the channels 22 and 24,the material so applied to the piston is machined so as to provide a smooth cylindrical surface of the hardened portion which is flush and co-terminus with the skirt of the piston. This material is then machined with grooves 30 to receive the piston rings 18, or at 32 to receive the piston rings 20.

A further and satisfactory method for preparing the pitson body before applying the hard material is depicted in Figs. 38.

In Fig. 3, there'is shown the piston it) after the wall 14 thereof has beengrooved to provide the upper and lower channels 22 and 24 for receiving the compression and oil rings respectively. These channels could be fabricated in the piston during their casting, or machined therein in any desired manner after the casting has been completed. In any event, the exposed surface portions 34 in the channel 22 and 36 in the channel 24 are roughened or serrated on both the bottom wallsand the side walls of the channels. These serrations provide a large number of points and irregular portions which are adapted to intimately engage the material of the hardened portions for interlocking as well as bonding the same to the pistons. As shown in the elevational view of Fig. 5, the serrated portions of the channels may be formed by knurling the surface of the Walls and bottom of the channels or in any other desired manner.

After the serrated portions are formed in the channels, molten molybdenum and stainless steel are sprayed successively into the channels as already described. Here again, after the spraying operation is completed, as shown in Fig. 7, the hardened body portions 26 and 28 will not only fill the channels 22 and 24 but will extend annularly and laterally therefrom to be ground off and machined as already described to provide ring grooves.

Upon the completion of the process, it will therefore be apparentthat the hard materials are intimately bonded in both secure mechanical and .efiicient heat transmitting relation to the heat conducting walls of the aluminum or other light weight piston. There is thus provided a wearing surface which is capable of withstanding the hammering of the hard piston rings, without sacrificmg the advantages of the light weight aluminum piston.

In some respects we are not able to account fully for the improved results attained and the relationship of elements established by the method and product of this 1nvention, and it should be understood that any attempt to analyze the theory which is believed to be responsible for these results is to be construed not as defining a mode of operation but merely as. a possible explanation of certain physical phenomena which have been observed. For instance, although the presence of the layer of ferrous aluminate is believed to come from precipitation of the vaporized aluminum on the molybdenum when the molybdenum 'is applied, its presence, aside from being apparently of benefit in the bonding, indicates that the molybdenum is bonded with pure aluminum. This is borne out by Fig. 15. There is no layer of aluminum oxide between the aluminum and molybdenum. The precipitation can be removed, if desired, before the stainless steel is applied and an excellent bonding relationship can be accomplished with the pure stainless steel on the molybdenum but the presence of the ferrous aluminate is preferred to pair with the aluminum as alternate layers of metals having substantially the same coefficient of heat expansion. 7

Then too, titanium, having a high boiling point, can be used also as an intermediate material in an oxygen free atmosphere. Consequently, the high melting points and boiling points of these two metals indicates that there is sufiicient heat present to vaporize the aluminum does not begin to precipitate until after the molybdenum or titanium begins to solidify and bond with the pure aluminum, thus assuring a bond between pure metals without contamination by the aluminum oxide. In fact, it can be expected that since the aluminum is melting and vaporizing just prior to the time the molybdenum begins to set and after a turbulent spraying application, the purity of the aluminum bonding to the molybdenum is assured even to a mixture of the molecules at the interface.

The intensity of the molecular action at the interfaces verse is equally advantageous because the high latent heat of vaporization requirements of the aluminum prevents too much vaporization of aluminum and also rapidly cools the molybdenum below its melting point at the interface so that the application, vaporization and cooling'occurring is substantially instantaneous above the approximate temperature of 262.0 C. and the molybdenum solidifies before the aluminum does at the interface. Thereby the harder metal is accommodated at the interface bonding by the aluminum solidifying subsequently at less tha 657 C. a

The stainless steel then melts the aluminum precipitate above 1535 C. but below' 2998 C., and the molecular activity results in ferrous aluminate if the aluminum has not been removed, and the bonding is completed.

Other metals also could serve as the intermediate material if their boiling point is high enough that aluminum is vaporized preferably without the metal reaching its own boiling point.

conditions, the calories per gram ratio between the metals being important. ent in the applied metal below its boiling point to cause some vaporization of the base metal at its surface.

We have found, however, that molybdenum gives the best results because some leeway is permitted in the distance between the nozzle of the metal spray gun and the work in order to control with predicability the vaporization and the resulting Brinell of the metal.

to 26 for grinding and groove cutting operations.

From the foregoing it will be seen how the various objectsof the invention are accomplished and how var' ions and further changes and modifications can be made without departing from the spirit of the invention, the scope of which is commensurate with the appended claims.

This application is a continuation-in-part application of our earlier filed application, Serial No. 392,164.

'What is claimed is:

1.,The method of bonding a light metal to a second comprising a metal selected from a group consisting of molybdenum, titanium, cobalt and nickel, including the steps of warming the light metal to a temperature above the boiling point of water but below its melting point; spraying the second metal against the light metal at a temperatureabove the boiling point of the light'metal and vaporizing a surface portion of the light metalto place the second metal into intimate bonding contact with the light metal in its pure state.

2. The method of bonding a light metal toa second metal comprising a metal selected from a group consisting of molybdenum, titanium, cobalt and nickel, includ-. ing the steps of spraying the second metal against the Cobalt and nickel could be used in this connection under carefully controlled temperature There should be enough calories pres- For the I filling 'metal a 3%." spacing gives the best degree of hardness which should be within the range or Rockwell C '23 3. The,method of bonding a plurality of metals togather including a light metal, a ferrous metal and an intermediate metal comprisinga metal selected from a the surface of said light metal, spraying said intermediate metal. against the light metal at a temperature above the boiling point of said light metal and vaporizing a surface portion thereof, precipitating the vaporized metal on the exposed surface of the intermediate metal, and bringing said ferrous metal in molten condition into contact, with said precipitated metal above the melting point thereof to form an alloy therewith.

4. Themethod of bonding aluminum and stainles steel together comprising spraying against said aluminum at a temperature above the boilingpoint of said aluminum, an intermediate metal comprising ;a metal selected from a group consistingof molybdenum, titanium, cobalt and nickel, vaporizing a surface portion of the aluminum to place the intermediate metal in intimate bonding contact with an unoxidized surface of said aluminum, and bringing the stainless steel in molten condition into contact with said sprayed intermediate metal.

5. The method of bonding a light metal and a ferrous metal together comprising spraying an intermediate metal against said light metal at a temperature above the boiling point of said light metal and with enough calories present forvaporizing a surface portion of the light metal to place the inter-mediatemetal in intimate bonding contact with an lunoxidized surface of said light metal, said intcrmediate metal comprising a metal selected from a group consisting of molybdenum, titanium, cobalt and nickel precipitating vaporizedlight metal on the exposed surface of the intermediate metal, and bringing theferrous metal in molten condition into contact with said sprayed intermediate .metalabove the melting point of any vaporized light. metal precipitated thereon to form an alloy therewith 6. The method of bondingyaluminurn and a ferrous metal together comprising spraying against said aluminum at a temperature above the boiling point thereof, an intermediate metal comprising a metal selected from a group consisting of molybdenum, titanium, cobalt and nickel, vaporizing, aluminum on the exposed surface of the intermediate metal, bringing the ferrous metal in molten condition, intocontact with said precipitated aluminum to form, a coating, of ferrous aluminate and applying a further coating; of the ferrous metal.

7. In a method of producing a lightweight piston of light metal having a ring receiving portion of ferrous metal provided in a circumferential channel upon the. exterior surface of the skirt of the light weight piston and having aring receiving groove therein, the improvement comprising first spraying in saidchannel a metal comprising a metal selected from the group consisting of molybdenum, titanium, cobalt and nickel at a temperature above the boiling point of the light metal, continuing said, spraying ,in said channel with said ferrous metal until an annular portion of the ferrous metal is formed which fillSlSal Cl channel and extends radially beyond the skirtof the: piston, andremoving from the annular portion sprayed metals extending radially beyond the piston skirt.

8. The method of claim 7 which includes the step of serrating the surface of the channel prior to the step of spraying said first sprayed metal.

9. The method of bonding a ferrous metal and a light metal comprising vaporizing a thin outer layer of said all) light metal with a deposited molten layer of a third metal selected from the group consisting of molybdenum, titanium, cobalt and nickel, precipitating the vaporized light metal on said deposited layer, and spraying theferrous metal against said third metal to form an alloy with said precipitated metal and as a continuing step spraying additional quantities of said ferrous metal upon said alloyed portion in pure form.

10. The method of bonding aluminum with a metal having a melting point above the boiling point of aluminum comprising vaporizing the surface layer of the aluminum with a thin layer of said metal, applying said metal to the aluminum surface remaining and solidifying the applied metal before said aluminum solidifies, said metal comprising a metal selected from the group consisting of molybdenum, titanium, cobalt and nickel.

11. The method of bonding light metal with a second metal comprising a metal selected from the group consisting of molybdenum, titanium, cobalt and nickel having a melting point above the boiling point of the light metal, said bonding including the steps of simultaneously generating at the surface of the light metal an atmosphere which includes vaporized light metal and molten particles of said second metal and depositing particles of said second metal in molten condition upon an unoxidized surface of said light metal within said atmosphere.

12. The method of bonding a light metal having a concave surface to a second metal comprising a metal selected from a group consisting of molybdenum, titanium, cobalt and nickel, including the steps of warmnig the light metalto a. temperature approximately 450 F., spraying the second metal into said concave surface and partially huddling said spray therein at a temperature above the boiling point of said light metal, and vaporizing a surface portion of said light metal in said concave surface to expose unoxidized light metal to said second metal for bond ing contact therewith.

13. The method of bonding a light metal having a concave surface to a second metal selected from the group consisting of molybdenum, titanium, cobalt and nickel. including the steps of toughening said concave surface, warming the light metal to a temperature above the boiling point of water but below its melting point, spraying the second metal against said roughened surface and partially huddling'said spray within said concave surface at a temperature above the boiling point of said light metal, and vaporizinglight metal from the roughened surface, generating an atmosphere including vaporized light metal and exposing .unoxidized light metal to contact with said second metal inbonding relationship.

14. The method of bonding aluminum and molybdenum together including the steps of warming aluminum to a temperature above the boiling point of water but below its melting point and spraying the molybdenum against the aluminum at a temperature above the 'boiling point of the aluminum and vaporizing the surface coating of aluminum oxide on the aluminum to place the molybdenum in intimate bonding contact with the aluminum metal in its pure state.

References Cited in the file of this patent UNITED STATES PATENTS Shepard Mar. 11, 1952 

3. THE METHOD OF BONDING A PLURALITY OF METALS TOGATHER INCLUDING A LIGHT METAL, A FERROUS METAL AND AN INTERMEDIATE METAL COMPRISING A METAL SELECTED FROM A GROUP CONSISTING OF MOLYBDENUM, TITANIUM, COBALT AND NICKEL, SAID METHOD INCLUDING THE STEPS OF ROUGHENING THE SURFACE OF SAID LIGHT METAL, SPRAYING SAID INTERMEDIATE METAL AGAINST THE LIGHT METAL AT A TEMPERATURE ABOVE THE BOILING POINT OF SAID LIGHT METAL AND VAPORIZING A SURFACE PORTION THEREOF, PRECIPITATING THE VAPORIZED METAL ON THE EXPOSED SURFACE OF THE INTERMEDIATE METAL, AND BRINGING SAID FERROUS METAL IN MOLTEN CONDITION INTO CONTACT WITH SAID PRECIPITATED METAL ABOVE THE MELTING POINT THEREOF TO FORM AN ALLOY THEREWITH. 